Cleaning appliances such as vacuum cleaners are well known. The majority of vacuum cleaners are either of the “upright” type or of the “cylinder” type (called canister or barrel machines in some countries). Cylinder vacuum cleaners generally comprise a main body which contains a motor-driven fan unit for drawing a dirt-bearing fluid flow into the vacuum cleaner, and separating apparatus, such as a cyclonic separator or a bag, for separating dirt and dust from the fluid flow. The dirt-bearing fluid flow is introduced to the main body through a suction hose and wand assembly which is connected to the main body. The main body of the vacuum cleaner is dragged along by the hose as a user moves around a room. A cleaning tool is attached to the remote end of the hose and wand assembly.
For example, GB 2,407,022 describes a cylinder vacuum cleaner having a chassis which supports cyclonic separating apparatus. The vacuum cleaner has two main wheels, one on each side of a rear portion of the chassis, and a castor wheel located beneath the front portion of the chassis which allow the vacuum cleaner to be dragged across a surface. Such a castor wheel tends be mounted on a circular support which is, in turn, rotatably mounted on the chassis to allow the castor wheel to swivel in response to a change in the direction in which the vacuum cleaner is dragged over the surface.
EP 1,129,657 describes a cylinder vacuum cleaner which is in the form of a spherical body connected to the suction hose and wand assembly. The spherical volume of the spherical body incorporates a pair of wheels, one located on each side of the body. The shape of the vacuum cleaner means that there is a tendency for the spherical body to rotate, or fall, on to one of the wheels over as it is pulled over a floor surface using the hose and wand assembly, and subsequently to be dragged uncontrollably over the surface. While the main body is arranged so that the centre of gravity of the main body is located in a position in which the main body will tend to return itself to an upright position, there is a risk that the main body may not be able to return to the upright position, for example if it is located against a wall or other item located on the floor surface